Continued investigations on the mechanisms of regulation of HMG-CoA reductase and acetyl-CoA carboxylase are proposed. In these studies we shall continue to study the ratio of active to inactive HMG-CoA reductase as a function of the nutritional or hormonal state of an animal. Emphasis will be placed on the short-term (10 to 60 min) effects of hormones on this ratio. These studies will utilize immunotitrations with antibody to HMG-CoA reductase. As conditions are found in which the ratio of active to inactive enzyme vary markedly, attempts will be made to identify the factors that effect this change in ratio and the mechanism of their action. We will also, in a related study, attempt to establish conditions under which the synthesis of HMC-CoA reductase can be demonstrated through the incorporation of a radioactive amino acid into newly synthesized enzyme. In our studies on the regulation of acetyl-CoA carboxylase activity we will attempt to purify the phosphatase that activates this enzyme to homogeneity. We will then prepare antibody to it and to the kinase that inactivates acetyl-CoA carboxylase. These antibodies will be used to determine the variations in the quantity and activity of the above kinase and phosphatase in livers of animals subjected to various nutritional and hormonal treatments. We will then attempt to determine the mechanisms of hormonal regulation of the activities of the kinase and phosphatase.